WO 2012068692 A1 describes a device for compacting a fiber material on a spinning machine, which device is intended for retrofitting on a conventional drafting system unit of the spinning machine. The device is disposed downstream of the drafting system unit of the spinning machine and is used to compact a fiber material discharged by the drafting system unit. Following the compaction device, the compacted fiber material, after passing through a nip point, is fed to a twist generation device. The twist generation device in a ring spinning machine, for example, consists of a traveler which revolves on a ring, wherein the yarn produced is wound onto a rotating tube.
The compaction device described in WO 2012068692 A1, for use on the usual twin drafting systems on ring spinning machines, comprises two driven and revolving suction drums which are acted upon by suction air and are rotatably supported on a support in an axially parallel manner and spaced from each other. Therefore, two suction drums are assigned as a unit (module) to one twin drafting system. The support comprises a suction channel connected to a negative pressure source, which suction channel is connected to the interior of the suction drums via appropriate inserts. The inserts are provided with appropriately shaped suction slits, whereby a corresponding air flow is generated at the periphery of the particular suction drum in a compaction zone. Protruding fibers are incorporated into the fiber material by means of this air flow which is oriented substantially transversely to the direction of transport of the fiber material.
Assigned to each of the suction drums is an annular drive element in the form of a friction wheel which rests via its circular inner surface, under the effect of a pressure load, on a portion of the circular peripheral surface of a projection disposed on the end face of the particular suction drum. The rotational motion of the friction wheel driven by friction on the outer periphery is transmitted to the peripheral surface of the projection which is connected to the suction drum. The friction wheel is driven via a frictional connection by the driven bottom delivery roller of the drafting system. Due to a closure cap fastened on the end of the projection, the friction wheel is held in position on the projection in the axial direction, wherein in the operating position, an axial gap is present between the end face of the suction drum and the friction wheel.
During the compaction process, individual fibers can detach from the fiber material to be compacted and settle on the periphery of the suction drum. These fibers can move in the direction of the end face of the suction drum and thereby pass into the axial gap between the end face of the suction drum and the friction wheel. The movement of fibers can be induced, for example, by the rotation of the suction drum or by the air flow produced by the rotation of the suction drum. There is a risk that fibers that pass into the axial gap will move to the outer periphery of the projection and adhere thereto. As a result, the inner surface of the friction wheel is no longer in direct contact with the outer periphery of the projection, whereby a continuous transmission of the drive torque from the friction wheel onto the suction drum is no longer ensured. As a result, the speed ratio between the suction drum and the bottom delivery roller of the drafting system changes. The fiber material to be compacted is therefore compressed in the compaction zone, which negatively affects the quality of the compaction of the fiber material. It is therefore necessary to move the drive element away from the suction drum after a certain operating time of the compaction device and remove the collected fibers from the outer periphery of the projection. This requires a great deal of maintenance effort and results in long downtimes of the spinning machine.